Synthesis, electrochemical and photophysical studies of the borondifluoride complex of a meta-linked biscurcuminoid†
Abstract
The synthesis of the borondifluoride complex of a biscurcuminoid system is described, and its electrochemical and photophysical properties are compared to those of a series of monochromophoric models. The data show that the meta-linked biscurcuminoid exhibits enhanced optical properties in solution, such as high optical brightnesses obtained at one- and two-photon excitation (B1 = 87 000 M−1 cm−1 and B2 = 313 GM, respectively). UV/visible absorption of solid-state particles formed in water solution revealed that the four investigated dyes are strongly aggregated and fluorescence spectroscopy showed that they are emissive in the NIR with fluorescence quantum yields spanning from 1.5 to 12.5%. In the case of the meta-linked biscurcuminoid, a high brightness is obtained using one- and two-photon excitation (B1 = 6952 M−1 cm−1 and B2 = 70 GM, respectively). Such red-shifted emission combined with a yet significant brightness in the solid-state is believed to arise from the choice of the meta-linkage which limits strong intermolecular packing.